1. Field of the Invention
This invention relates to a thermoplastic resin composition having superior chemical resistance and impact resistance, and, in particular, to a thermoplastic resin composition with superior chemical resistance and impact resistance, to which an aromatic polyester and an aromatic polycarbonate are compounded, and in which a thermoplastic resin containing .alpha.-methyl styrene is used.
2. Description of the Background
Conventionally, aromatic vinyl thermoplastic resins, rubber-modified styrene thermoplastic resins, in particular, have widely been used in a variety of fields for automobile parts, electric appliances, and the like, because they are light in weight and have superior moldability.
However, rubber-modified styrene thermoplastic resins are not always stable against organic solvents or the like. Moreover, their chemical resistances are sometimes significantly impaired when a stress is involved or when the article is used in deformed conditions. These present a big problem when one contemplates to use a rubber-modified styrene thermoplastic resin for diversified applications.
Especially, when the resin is used as an automobile part which may contact with a polyvinyl chloride resin to which a plasticizer is compounded or when break fluid sticks to the rubber-modified styrene thermoplastic resin part, the resin develops so-called environmental stress crack.
In order to overcome these problems, attempts have been undertaken such as to increase the molecular weight of a rubber-modified styrene thermoplastic resin or to introduce a vinylcyano compound or a monomer having a polar group such as (meth)acrylic acid ester into the resin polymer. These attempts, however, are not successful in providing sufficient chemical resistance to rubber-modified styrene thermoplastic resins.
Furthermore, rubber-modified styrene thermoplastic resins do not possess sufficient impact resistance, and therefore their fields of application have been limited in this respect.
The inventors have undertaken extensive studies in order to resolve these problems in rubber-modified styrene thermoplastic resins, and found that a resin having remarkably improved chemical resistance and impact resistance can be obtained by using a rubber-modified styrene thermoplastic resin to which specific amounts of .alpha.-methyl styrene is copolymerized and by compounding a specific amount of aromatic polyester and aromatic polycarbonate into this rubber-modified styrene thermoplastic resin. The finding has led to the completion of this invention.